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testing a main vent

zepfanzepfan Posts: 266Member
what is the best way to tell if a main vent on a two pipe system is plugged up without burning yourself? just slowly unscrew it till you get steam and no air? i need to go look at a steam system on tuesday where the problem is several radiators on the top floor don't get hot and haven't for about ten years.i am suspecting a plugged main vent or too low of pressure.steam systems are very rare in our area.


  • gerry gillgerry gill Posts: 2,951Member
    turn off the system,

    then unscrew the vent, and holding the vent vertical, blow up into it..if your cheeks puff out from backpressure she most likely is no good anymore..if you can easily blow thru it, then it is probably so other issue that is effecting your rads.

    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • crash2009crash2009 Posts: 1,484Member
    Shut off the system

      Gerry explained stuck closed, I will attempt to explain stuck open.  Remove the vent.  Turn the vent upside down, keeping it verticle, blow into it.  If air will pass, this is stuck open.  If the vent fails either test, sell them a new one.  For a look at whats inside those vents click on this
  • Dave in QCADave in QCA Posts: 1,737Member
    More information needed

    It might be best if you take pictures, make observations, then come back to the wall.

    My first thoughts are that I have never seen nor heard of a steam main getting plugged up.   Also, raising the pressure setting is the sign of an attempt to fix a system that is not working, withouth correcting the actual problem.  Usually, the increased pressue causes more problems than it fixes.  DON"T raise the pressure.  Residential systems operate at 2 PSI max.   Most operate quite well at 0.5 psi.
    Dave in Quad Cities, America
    Weil-McLain 680 with Riello 2-stage burner, December 2012. Firing rate=375MBH Low, 690MBH Hi.
    System = Early Dunham 2-pipe Vacuo-Vapor (inlet and outlet both at bottom of radiators) Traps are Dunham #2 rebuilt w. Barnes-Jones Cage Units, Dunham-Bush 1E, Mepco 1E, and Armstrong TS-2. All valves haveTunstall orifices sized at 8 oz.
    Current connected load EDR= 1,259 sq ft, Original system EDR = 2,100 sq ft Vaporstat, 13 oz cutout, 4 oz cutin - Temp. control Tekmar 279.
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